D I A 



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DIG 



DI'APHRAGM:. (Sutyparffw,, Gr. dia- 

 pkragma, Lat. diaphragme, Fr. 

 diafragma, It.) A large transverse 

 muscle, which separates the chest 

 from the belly ; the midriff. 



DIA'SPORE. (from BiaffTrelptv, Gr. to 

 disperse.) This name has been 

 assigned to the mineral from the 

 peculiarity that when exposed to 

 heat it decrepitates violently, and 

 is dispersed in numerous small 

 spangles. It is a rare mineral and 

 but little known : it is a combi- 

 nation of alumina and water, often 

 mixed with hydrate of iron . Speci - 

 fie gravity 3 -43. 



DlATOMOUS SCHILLER SPAR, (from Sia, 



through, and re/ii/a?, to cut, Gr. 

 from being easily cleavable in one 

 direction. The schillerstein of 

 "Werner ; diatomer schiller-spath 

 of Mohs ; diallage chatoyante of 

 Broehant.) An earthy mineral, a 

 combination of bisilicate of mag- 

 nesia, protoxide of lime and iron, 

 with hydrate of magnesia. It is 

 prismatic. Cleavage in two direc- 

 tions, forming together an angle of 

 about 135; one cleavage perfect 

 and easily obtained, the other ap- 

 pearing only in traces. Hardness 

 = 3-5, 4, Specific gravity = 

 2-6 2-8. Its colours are green, 

 grey, and brown. Occurs in granu- 

 lar concretions ; disseminated, and 

 seldom massive. Lustre shining 

 or splendent, and metallic pearly. 

 Opaque, and yields to the knife. 

 Streak greyish or yellowish white, 

 dull. Before the blow-pipe it 

 becomes hard, and assumes a me- 

 tallic appearance. Occurs in ser- 

 pentine and greenstone and in 

 secondary trap rocks. Jameson. 

 Phillips. 



DIBRA'NCHIATA. The first order in 

 the class Cephalopora. This order, 

 called by Pictet Cephalopoda Ace- 

 tabularia, has been divided by 

 him into two sub-orders, Octoheda, 

 and Docanida. 



DI'CERAS. (from and Kcpa?, Gr.) 



A genus of fossil shells discovered 

 in oolitic rocks. At Mount Saleve, 

 near Geneva, two species have been 

 discovered, but the genus has not 

 been met with in England, it is 

 thus named from possessing two 

 prominent spiral umbones, which 

 resemble two twisted horns. 



DICHOBTJNE. (from $i'x a ) bipartitio, 

 and powos, collis, Gr.) This genus 

 was proposed by Cuvier instead of 

 Anoplotherium minus. It is closely 

 allied to the Anoplotherioid genus 

 Xiphodon, the dental formula is 

 the same, only there is a slight 

 interval between the canine and 

 the first premolar in both jaws: 

 the first three premolars are sub- 

 compressed, sub-trenchant, but less 

 elongated from behind forwards 

 than in Xiphodon. Owen. The 

 dichobune has points, arranged in 

 pairs, on the back molars of the 

 lower jaw. It has been found 

 fossil only, and in strata more 

 recent than the chalk. 



DICHO'TOMOTTS. (from /x a an< ^ T6ytn/ftj, 

 Gr. dichotome, Fr. dicotomo, It.) 

 Forked ; regularly and continually 

 divided by pairs from the top to 

 the bottom : applied to stems divi- 

 ding into two parts ; example, the 

 misletoe. 



DicfnoDox. The name of a genus 

 of extinct Artiodactyle Mammals 

 of the Eocene period. A portion 

 of the upper jaw of a species Dich- 

 odon Cuspidatus is in the British 

 Museum, as also a portion of a 

 lower jaw. 



Dicn'ROigM. A term used in miner- 

 alogy to express a property 

 possessed by some bodies of ex- 

 hibiting different colours, when 

 examined by transmitted light, in 

 determinate directions. lolite, 

 tourmaline, and mica possess this 

 property. 



DI'CHROIT. | (Of Greek etymology, 



DI'CHROITE. j implying double co- 

 lour, because its crystals present a 

 very deep blue when viewed in a 



